During the premiere of Katie Couric's talk show, Katie, Sheryl explained, "There are no doctors that will confirm that, [but] I do have the theory that it's possible that it's related to that. I [used to spend] hours on the old, archaic cell phones."

The tumor in her brain is located near her ear, where she used to hold her phone. As for the early symptoms, the mom of two boys revealed that she suspected something was up when she started forgetting lyrics onstage and feeling "mushy."